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A fire fighter douse water after flames from the Mosquito Fire jumped the American River, burning structures in Volcanoville, Calif on September 10, 2022. The fast-moving Mosquito Fire in the Sierra Nevada foothills doubled in size Friday to at least 46 square miles and threatened 3,600 homes, while blanketing the region in smoke.

Fire fighters cut burned tree trunks after flames from the Mosquito Fire jumped the American River, burning structures in Volcanoville, Calif on September 10, 2022. The fast-moving Mosquito Fire in the Sierra Nevada foothills doubled in size Friday to at least 46 square miles and threatened 3,600 homes, while blanketing the region in smoke.

Firefighters made progress early Sunday against the Mosquito Fire in the Sierra foothills, aided by cooler temperatures and increased humidity — though the pall of smoke also helping to reduce fire activity pushed air quality to hazardous levels north and east of the fire past the Nevada border.

The blaze, which sparked Tuesday near Foresthill and is burning in Tahoe and El Dorado national forests between Sacramento and Tahoe, had consumed 41,443 acres and was 10% contained Sunday morning, Cal Fire said in an online update.

The Mosquito Fire is the largest wildfire Cal Fire has handled so far this year, according to the agency’s records — though it is far smaller than the record-smashing blazes of other recent seasons. At No. 1 is the August Complex, which charred more than 1 million acres in 2020.

The Mosquito Fire has forced the evacuation of 11,117 people, the Placer County Sheriff’s Office said Sunday on Twitter.

After generating a giant pyrocumulus cloud, the fire continued to pump smoke across a large swath of Northern California.

Air quality Sunday morning ranged from unhealthy to hazardous from Sacramento north to Redding and across the Sierra from Yosemite through Tahoe and past the northern borders of California and Nevada, according to the Sacramento office of the National Weather Service and the online airnow.gov air quality map.

Weather officials on Twitter urged residents to monitor air quality and “stay indoors if possible & use an air filter” in areas where conditions were unhealthy.

Air quality at 8:30 am this morning ranged from Moderate to Hazardous across the area due to wildfire smoke. Stay indoors if possible & use an air filter. For current air quality readings go to https://t.co/aU5y5CyfhS or check with your local air quality district. #CAwx pic.twitter.com/kAyALpuH5u

In South Lake Tahoe, the air quality index was at the “very unhealthy” level Sunday morning.

“It’s pretty nasty out there,” said Wendy Davis, a cashier at Heidi’s Pancake House, in a phone interview.

The restaurant does not have outdoor seating, but Davis said people in South Lake Tahoe were staying indoors to escape the murky weather conditions.

The smoke was so potent over the weekend that some hotels reported more cancellations.

At the waterfront Beach Retreat & Lodge at Tahoe, managers told The Chronicle there were 100 cancellations over 24-hour period Friday. Guests have been checking out early this weekend as well, or choosing to remain indoors.

Managers said the smoke rivaled last year when the nearby Caldor Fire threatened and prompted evacuations in the South Lake Tahoe area. The Caldor Fire charred more than 221,800 acres southeast of South Lake Tahoe.

While the cloudy, cooler weather this weekend resulting from the remnants of Hurricane Kay after last week’s brutal Western heat wave was working in firefighters’ favor, the benefits were likely to be “slight and brief,” Cal Fire said Sunday. Brush, timber and other vegetation in the area that feeds the fire is “critically dry,” officials said.

Southwest winds Sunday afternoon were expected to lift the smoke inversion, creating better ventilation to fan the flames, fire officials said, and thunderstorms were forecast to the east of the fire along the Sierra Crest — creating the potential for lightning strikes.

Winds already were picking up Sunday morning, contributing to the fire’s spread to the north and northeast of communities in Foresthill, and new evacuation orders and warnings were added to those already in place in both Placer and El Dorado counties.

Most of tiny Volcanoville’s 231 residents had fled by Saturday, with fire crews remaining to protect structures. The fire destroyed several structures along Volcanoville Road, although official tallies had yet to indicate any lost buildings.

Approximately 5,850 homes remain threatened, according to the Placer County Sheriff’s Office.

Evacuation centers were set up in Placer County at Sierra College in Rocklin; and in El Dorado County at Cameron Park Services District in Cameron Park, and Green Valley Community Church in Placerville.

Animal evacuation centers were open in Placer County at the Animal Services Center in Auburn, and the Nevada County Fairgrounds in Grass Valley; and in El Dorado County, at the Diamond Springs Shelter in Diamond Springs and the Flying M Ranch in Placerville.

No cause has yet been determined for the Mosquito Fire, though PG&E has reported “electrical activity” on a nearby transmission line around the start of the fire.

Anna Buchmann and Jessica Flores are San Francisco Chronicle staff writers. Email: anna.buchmann@sfchronicle.com, jessica.flores@sfchronicle.com Twitter: @AnnaBGedit, @jesssmflores

Anna Buchmann is The San Francisco Chronicle's engagement editor. She joined the newsroom staff in 2019 as an online producer for SFChronicle.com. Previously, she worked at The Sacramento Bee in a variety of roles, including digital senior editor, senior editor for topics and breaking news, regional news desk director and copy desk chief. She also trained newsroom reporting interns in the fundamentals of journalism. Buchmann began her journalism career at the San Jose Mercury News, where her roles included news editor, wire editor, copy editor, page designer and education reporter. She earned her bachelor's degree in English literature from Georgetown University and her master's degree in journalism from Stanford University, where she also taught editing in the journalism M.A. program.

Jessica Flores is a reporter for The San Francisco Chronicle. Before joining The Chronicle in 2021, she worked for USA Today, NPR affiliate KPCC and Curbed LA. Originally from L.A., she received her master's degree in journalism from the University of Southern California and a bachelor's degree from Mount Saint Mary's University in Los Angeles.